modify changes from CNY-818 to be backwards compatible - if buildFlavor passed in is None, we must not set recipeClass._buildFlavor or rely on new behavior.
modify changes from CNY-818 to be backwards compatible - if buildFlavor passed
in is None, we must not set recipeClass._buildFlavor or rely on new behavior.

fedora-conary/conary,fedora-conary/conary,fedora-conary/conary,fedora-conary/conary,fedora-conary/conary